104 DISTRIBUTION AND MOVEMENTS OF DESERT PLANTS. 
Agriculture and Mechanic Arts, has worked over the various members 
of the family Allionacea, on which group he is preparing a publication. 
Prof. H. M. Hall, of the University of California, has verified the names 
of miscellaneous plants from time to time from this locality. 
TABLE 11.— Showing the Various Spectes from Standpoints of Habitat and Vegetation Form. 














igi: II. Tis erie 
| Santa 
| se Santas) (Cruz. Intros 
Vegetation forms. _ Tuma- nome roe Rivér | duced” Total. 
moc Hill. AGE. flood- | and irri-| species. 
plain gation 
| SlOpee: 4 ditches. | 
| ele af 
‘Thees sign be. eae eee | 2 2 UHL , SASS E ae Ate eke 15 
 SHCODS chee 8 eee ee ee | 16 IO LO es sree 3 39 
W Oody twiners-..-) ee RDA per ae Ml Reet eto a? by 3 5 
Jowartshrabs (io). | ra ES SEO es ere BR ey ee, ed 17 
Hali-chrubs< reetage | On al Tek Wa ere I 2 
\iPerennialtherbers., -aakoeoe <i, 2410) ae 7 108 
}) Brenmial hers a. Ses, See | ‘2% I a Wh beer, HAE et eee 3 
Annual herbs: 
(a) Long-lived”... 2.» aes? | 9 250 Whar 2 2 57 
(b) Winter annuals... .| 38 46 TOUeI Se he Be 122 
(c) Summer annuals... 7 25 Ad os ee a 44 
Algae Gat aaa ae le oo I SS Sekar Ih ecgeeeae ene een Po eee et rm 
Total ee eee eed 138 | 128 ri7 T4 52 449 
The data in table 11 suggest some interesting observations. It may 
be taken as almost axiomatic that biennial species are not a success in 
our region. The intense conditions prevailing regularly over a consid- 
erable portion of the year, together with occasional prolonged droughts, 
render their existence almost impossible. Either our plants develop 
root-systems extensive and permanent enough to endure for some years, 
as in the case of many perennial herbs and of all the suffrutescent and 
woody forms; or else their growth is completed within the course ofa 
few weeks, or at most a few months, during those portions of the year 
when mesophytic conditions prevail to some extent over the country. 
There appears to be little middle ground in this matter. In areas I and 
II, where the most pronounced xerophytic conditions obtain, the woody 
species, including trees, shrubs, dwarf shrubs, half shrubs, and woody 
twiners, constitute 30 per cent of the plants. It needs hardly be said 
that to these plant-types belong our characteristic desert fornis. 
The short-lived winter annual and summer annual species, on the 
other hand, make up 43 per cent of the plants of these same two areas. 
That these plants are unable to withstand arid conditions may be in- 
ferred from the fact that with their first approach they cease further 
growth and begin dying. Such species as Phacelia distans, Ellisia torreyi, 
Pectocarya linearis, and Harpagonella palmeri die off in early spring, 
except in the shade of bushes, even with the presence of considerable 
